Keep in mind that unless the same data exists in at least two locations, it's one electromagnetic pulse away from oblivion. I've learned the hard way to be fanatical about backing up EVERYTHING. To answer your question, absolutely back up your runtime directory. If you restore your backup to its original location, should have no path problems.

I recommend you keep system and data directories on seperate hard drives, which will minimise the likelihood of losing your data should your system fail. I keep all my Poser stuff on a dedicated HD, including the app itself. This allows the transfer of ALL things Poser to any number of backup disks, and lets me jump right back into Poser without having to reinstall the app. If you go this route, you'll want to get a copy of Correct Reference by Hogsoft, to keep your data paths coherent should your root directory change. I use CR Pro, bu I think there's a free version available.

My rule is to have double the HD capacity I use for actual computing, so that all active disks are backed up. Some backups I store at the office should the house burn down. You can get away with less than double capacity if you use a compressive backup prog like Acronis True Image.

All that extra HD capacity might seem like expensive overkill, but hard disks are cheap compared to wasting your time reinstalling, and are DEAD CHEAP compared to losing thousands of hours of work.

Good luck!